FCER1A and allergic disease: However, equine IgE-binding monocytes bound similar densities of IgE on their surface, regardless of clinical signs of allergy or environmental exposure to Cul. We expect that IgE MFI directly correlates to surface density of FcεRI because IgE readily sensitizes FcεRI+ cells by binding to the receptor independently from specific allergen/ligand binding at a FcεRIα chain to IgE ratio of 1:1 [23,52].